Electricity: measuring and testing – Fault detecting in electric circuits and of electric components – Of individual circuit component or element
Reexamination Certificate
2000-12-12
2001-10-02
Karlsen, Ernest (Department: 2858)
Electricity: measuring and testing
Fault detecting in electric circuits and of electric components
Of individual circuit component or element
C324S755090
Reexamination Certificate
active
06297660
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to semiconductor manufacture, and more particularly to an improved test carrier for temporarily packaging and testing semiconductor components, such as bare dice and chip scale packages. This invention also relates to a test system incorporating the carrier, and to test methods employing the carrier.
BACKGROUND OF THE INVENTION
Semiconductor components, such as bare dice and chip scale packages, must be tested prior to shipment by semiconductor manufacturers. Since these components are relatively small and fragile, carriers have been developed for temporarily packaging the components for testing. The carriers permit electrical connections to be made between external contacts on the components, and testing equipment such as burn-in boards. On bare dice, the external contacts typically comprise planar or bumped bond pads. On chip scale packages, the external contacts typically comprise solder balls in a dense array, such as a ball grid array, or a fine ball grid array.
An interconnect component of the carrier includes contacts that make the temporary electrical connections with the external contacts on the components. The interconnect provides power, ground and signal paths to the component. A force applying mechanism of the carrier applies a biasing force for biasing the component against the interconnect. Typically, the force applying mechanism includes a biasing member such as a metal, or elastomeric spring for applying the biasing force. In addition, the force applying mechanism can include a clamp, or a latch plate, for securing the biasing member to a base of the carrier.
One aspect of this type of carrier is that the biasing force is determined by the geometry and construction of the force applying mechanism. This biasing force is fixed when the carrier is assembled, and the biasing member presses the component against the interconnect. However, it would be advantageous to be able to adjust this biasing force during and subsequent to assembly of the carrier.
For example, a relatively large biasing force is required during initial contact of the component with the interconnect. The large biasing force is required for making reliable temporary electrical connections with the contacts on the component. Solder balls, for example, can be retained in a conductive pocket, or penetrated with conductive projections. The large biasing force is necessary for penetrating native oxide layers present to make low resistance electrical connections. However, once the electrical connections are made with the component contacts, the biasing force does not need to be as large. Also, if the carrier and component are heated during testing, such as in a burn-in oven, the contacts expand, and lower biasing forces are sufficient to maintain the electrical connections.
The present invention is directed to a carrier that includes a biasing member constructed to provide a variable biasing force. In particular, the biasing force can be large during initial assembly of the carrier, and smaller following assembly and during operation of the carrier.
SUMMARY OF THE INVENTION
In accordance with the present invention, an improved test carrier, an improved test system incorporating the carrier, and an improved test method employing the carrier, are provided. The test carrier can be used to temporarily package and test semiconductor components, such as bare dice, and chip scale packages. The carrier includes a base for retaining one or more components, and an interconnect having contacts for making temporary electrical connections with contacts on the component. The carrier also includes a force applying mechanism for biasing the component against the interconnect. The force applying mechanism includes a biasing member formed of an elastomeric material such as silicone, butyl rubber, fluorosilicone, and polyimide. The biasing member is configured to apply a relatively large biasing force during assembly of the carrier, and a smaller biasing force in the assembled carrier.
The variable biasing force is achieved by the geometry of the biasing member. Specifically, compression of the biasing member by a sufficient amount changes the shape of the biasing member, and causes the biasing force to be greater for each increment of compression.
In a first embodiment, the biasing member comprises a tubular element that is flattened during assembly of the carrier. Flattening of the biasing member provides a relatively large biasing force with each increment of compression, such that reliable electrical connections are made between contacts on the interconnect and the component during assembly of the carrier. During assembly, flattening and compression of the biasing member is achieved by overdriving the biasing member in the z-direction using an assembly tool. Following assembly, the biasing member returns to a tubular shape in the assembled carrier, such that a smaller biasing force is exerted with each increment of compression. In the assembled carrier the amount of compression of the biasing member is fixed by the geometry of the carrier and biasing member. These geometries can be selected to provide a biasing force that is just large enough to maintain reliable electrical connections with the component during burn-in and other tests procedures.
In a second embodiment, the biasing member has a wave shape. The biasing member is flattened during assembly of the carrier, then returns to the wave shape in the assembled carrier. In a third embodiment, the biasing member has an accordion shape. Again, the biasing member is flattened during assembly of the carrier, then returns to the accordion shape in the assembled carrier. In both embodiments the biasing force with each compressive increment varies, depending on the shape of the biasing member.
In addition to the biasing member, the force applying mechanism includes a clamp which attaches to the base, and a pressure plate which is pressed by the biasing member against the component. The pressure plate can include an elastomeric layer for evenly applying the biasing force exerted by the biasing member to the component. In addition, the elastomeric layer can include a metal or polymer outer layer, which prevents adhesion of the elastomeric layer to the surface of the component. Further, the elastomeric layer, pressure plate and biasing member can comprise electrically conductive materials, to provide an electrical path from a backside of the component during testing. One suitable conductive material for the elastomeric layer and biasing member comprises silicone filled with graphite or metal particles.
A method for testing a component in accordance with the invention includes the initial step of providing a carrier comprising a base, an interconnect, and a force applying mechanism having a biasing member configured to exert a variable biasing force. The method also includes the step of assembling the carrier by flattening the biasing member in the z-direction, to provide a relatively large biasing force for making electrical connections between contacts on the component and the interconnect. Following the assembly step, the method includes the step of allowing the biasing member to expand in the z-direction in the assembled carrier, to provide a smaller biasing force for testing the component.
A test system constructed in accordance with the invention includes the carrier and test circuitry. The test circuitry generates and transmits test signals through the carrier to the component, and evaluates the resultant signals. The test system can also include a burn-in board which provides electrical interface between the carrier and test circuitry.
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Akram Salman
Farnworth Warren M.
Gochnour Derek
Wark James M.
Gratton Stephan A.
Karlsen Ernest
Micro)n Technology, Inc.
Tang Minh
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